1#!/usr/bin/env python 2 3import string 4import struct 5import sys 6 7 8class FileExtract: 9 '''Decode binary data from a file''' 10 11 def __init__(self, f, b='='): 12 '''Initialize with an open binary file and optional byte order''' 13 14 self.file = f 15 self.byte_order = b 16 self.offsets = list() 17 18 def set_byte_order(self, b): 19 '''Set the byte order, valid values are "big", "little", "swap", "native", "<", ">", "@", "="''' 20 if b == 'big': 21 self.byte_order = '>' 22 elif b == 'little': 23 self.byte_order = '<' 24 elif b == 'swap': 25 # swap what ever the current byte order is 26 self.byte_order = swap_unpack_char() 27 elif b == 'native': 28 self.byte_order = '=' 29 elif b == '<' or b == '>' or b == '@' or b == '=': 30 self.byte_order = b 31 else: 32 print("error: invalid byte order specified: '%s'" % b) 33 34 def is_in_memory(self): 35 return False 36 37 def seek(self, offset, whence=0): 38 if self.file: 39 return self.file.seek(offset, whence) 40 raise ValueError 41 42 def tell(self): 43 if self.file: 44 return self.file.tell() 45 raise ValueError 46 47 def read_size(self, byte_size): 48 s = self.file.read(byte_size) 49 if len(s) != byte_size: 50 return None 51 return s 52 53 def push_offset_and_seek(self, offset): 54 '''Push the current file offset and seek to "offset"''' 55 self.offsets.append(self.file.tell()) 56 self.file.seek(offset, 0) 57 58 def pop_offset_and_seek(self): 59 '''Pop a previously pushed file offset, or do nothing if there were no previously pushed offsets''' 60 if len(self.offsets) > 0: 61 self.file.seek(self.offsets.pop()) 62 63 def get_sint8(self, fail_value=0): 64 '''Extract a single int8_t from the binary file at the current file position, returns a single integer''' 65 s = self.read_size(1) 66 if s: 67 v, = struct.unpack(self.byte_order + 'b', s) 68 return v 69 else: 70 return fail_value 71 72 def get_uint8(self, fail_value=0): 73 '''Extract a single uint8_t from the binary file at the current file position, returns a single integer''' 74 s = self.read_size(1) 75 if s: 76 v, = struct.unpack(self.byte_order + 'B', s) 77 return v 78 else: 79 return fail_value 80 81 def get_sint16(self, fail_value=0): 82 '''Extract a single int16_t from the binary file at the current file position, returns a single integer''' 83 s = self.read_size(2) 84 if s: 85 v, = struct.unpack(self.byte_order + 'h', s) 86 return v 87 else: 88 return fail_value 89 90 def get_uint16(self, fail_value=0): 91 '''Extract a single uint16_t from the binary file at the current file position, returns a single integer''' 92 s = self.read_size(2) 93 if s: 94 v, = struct.unpack(self.byte_order + 'H', s) 95 return v 96 else: 97 return fail_value 98 99 def get_sint32(self, fail_value=0): 100 '''Extract a single int32_t from the binary file at the current file position, returns a single integer''' 101 s = self.read_size(4) 102 if s: 103 v, = struct.unpack(self.byte_order + 'i', s) 104 return v 105 else: 106 return fail_value 107 108 def get_uint32(self, fail_value=0): 109 '''Extract a single uint32_t from the binary file at the current file position, returns a single integer''' 110 s = self.read_size(4) 111 if s: 112 v, = struct.unpack(self.byte_order + 'I', s) 113 return v 114 else: 115 return fail_value 116 117 def get_sint64(self, fail_value=0): 118 '''Extract a single int64_t from the binary file at the current file position, returns a single integer''' 119 s = self.read_size(8) 120 if s: 121 v, = struct.unpack(self.byte_order + 'q', s) 122 return v 123 else: 124 return fail_value 125 126 def get_uint64(self, fail_value=0): 127 '''Extract a single uint64_t from the binary file at the current file position, returns a single integer''' 128 s = self.read_size(8) 129 if s: 130 v, = struct.unpack(self.byte_order + 'Q', s) 131 return v 132 else: 133 return fail_value 134 135 def get_fixed_length_c_string( 136 self, 137 n, 138 fail_value='', 139 isprint_only_with_space_padding=False): 140 '''Extract a single fixed length C string from the binary file at the current file position, returns a single C string''' 141 s = self.read_size(n) 142 if s: 143 cstr, = struct.unpack(self.byte_order + ("%i" % n) + 's', s) 144 # Strip trialing NULLs 145 cstr = string.strip(cstr, "\0") 146 if isprint_only_with_space_padding: 147 for c in cstr: 148 if c in string.printable or ord(c) == 0: 149 continue 150 return fail_value 151 return cstr 152 else: 153 return fail_value 154 155 def get_c_string(self): 156 '''Extract a single NULL terminated C string from the binary file at the current file position, returns a single C string''' 157 cstr = '' 158 byte = self.get_uint8() 159 while byte != 0: 160 cstr += "%c" % byte 161 byte = self.get_uint8() 162 return cstr 163 164 def get_n_sint8(self, n, fail_value=0): 165 '''Extract "n" int8_t integers from the binary file at the current file position, returns a list of integers''' 166 s = self.read_size(n) 167 if s: 168 return struct.unpack(self.byte_order + ("%u" % n) + 'b', s) 169 else: 170 return (fail_value,) * n 171 172 def get_n_uint8(self, n, fail_value=0): 173 '''Extract "n" uint8_t integers from the binary file at the current file position, returns a list of integers''' 174 s = self.read_size(n) 175 if s: 176 return struct.unpack(self.byte_order + ("%u" % n) + 'B', s) 177 else: 178 return (fail_value,) * n 179 180 def get_n_sint16(self, n, fail_value=0): 181 '''Extract "n" int16_t integers from the binary file at the current file position, returns a list of integers''' 182 s = self.read_size(2 * n) 183 if s: 184 return struct.unpack(self.byte_order + ("%u" % n) + 'h', s) 185 else: 186 return (fail_value,) * n 187 188 def get_n_uint16(self, n, fail_value=0): 189 '''Extract "n" uint16_t integers from the binary file at the current file position, returns a list of integers''' 190 s = self.read_size(2 * n) 191 if s: 192 return struct.unpack(self.byte_order + ("%u" % n) + 'H', s) 193 else: 194 return (fail_value,) * n 195 196 def get_n_sint32(self, n, fail_value=0): 197 '''Extract "n" int32_t integers from the binary file at the current file position, returns a list of integers''' 198 s = self.read_size(4 * n) 199 if s: 200 return struct.unpack(self.byte_order + ("%u" % n) + 'i', s) 201 else: 202 return (fail_value,) * n 203 204 def get_n_uint32(self, n, fail_value=0): 205 '''Extract "n" uint32_t integers from the binary file at the current file position, returns a list of integers''' 206 s = self.read_size(4 * n) 207 if s: 208 return struct.unpack(self.byte_order + ("%u" % n) + 'I', s) 209 else: 210 return (fail_value,) * n 211 212 def get_n_sint64(self, n, fail_value=0): 213 '''Extract "n" int64_t integers from the binary file at the current file position, returns a list of integers''' 214 s = self.read_size(8 * n) 215 if s: 216 return struct.unpack(self.byte_order + ("%u" % n) + 'q', s) 217 else: 218 return (fail_value,) * n 219 220 def get_n_uint64(self, n, fail_value=0): 221 '''Extract "n" uint64_t integers from the binary file at the current file position, returns a list of integers''' 222 s = self.read_size(8 * n) 223 if s: 224 return struct.unpack(self.byte_order + ("%u" % n) + 'Q', s) 225 else: 226 return (fail_value,) * n 227